Active control of noise generated by airfoils, and in particular noise generated by airfoils in serially arranged cascades of rotating and stationary airfoils such as maybe found in the compressor or turbine section of a gas turbine engine, has recently received increased attention by the designers and manufacturers of such engines. One significant component of the noise generated in these engines is caused by the interaction between the moving pressure wake extending downstream from each of the moving airfoil blades and the leading edges of each of the stationary airfoil vanes. The wake, which includes both pressure and velocity fluctuations strikes the leading edge of the downstream stator vane, resulting in the generation of an acoustic pressure wave which, in certain frequency ranges, is perceived as noise.
Methods of attenuating this acoustic noise generated in the engine have included sound absorbing liners, mixers, and other devices to absorb or otherwise contain the generated noise within the gas turbine engine or its surrounding enclosure.
While such methods have been somewhat effective, there remains a need for further, effective reduction of the acoustic noise generated by the interaction of the trailing wakes and stator vane leading edges.